Inlet guide vane actuating arrangement for multistage centrifugal compressor



Aug. 19, 1969 c, HOFFMAN ET AL 3,461,685

' mm-rr uuwm VANI-J ACTUATING ARRANGEMENT FOR MULTIS'IAGE CBNTRIFIJGAIJCOMPRESSOR Filed Aug.

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INVENTORS DAVID C. HOFFMAN WYMAN K.

[ENDER BMLAN WOLD ATTORNEY Afig. 19, 1969 D, Q HOFFMAN ETAL 3,461,685

INLET GUIDE VANE ACTUA'IING ARRANGEMENT FOR MULTISTAGE CEN'IRTF'UGALCOMPRESSOR I5 Sheets-Sheet 2 Filed Aug.

FIG. 4

I NVENTOR 5 DAVID C. HOFFMAN WYMAN K. EHDER ALLAN I. WOLD m 0 W ATTORNEYAug. '19, 1 969 c op ETAL 3,461,685

INLET GUIDE vmm ACTUATING ARRANGEMENT FOR MULTIS'IAGE CENIHIFUGALCOMPRESSOR Filed Aug. 2, 1967 s Sheets-Sheet s FIGJ5 IOO INVENTORS DAVIDc. HOFFMAN WYMAN K. ENDER B ALLAN I. wow

ATTOIRNEY United States Patent U.S. Cl. 62-510 10 Claims ABSTRACT OF THEDISCLOSURE A multiple stage refrigerant compressor is provided withadjustable guide vanes at the inlet to each stage of compression, withthe linkage mechanism for each set of guide vanes being actuated by acommon operating shaft which extends through the compressor casing atonly one point. The guide vane operating shaft section for an advancedstage of compression extends axially of the compressor casing outside ofthe interstage crossover passage, thereby minimizing the number of sealsrequired along the operating shaft. The linkage mechanism for theadvanced stage adjustable guide vanes is located in a chamber which alsoserves as a plenum space from which economizer gas is injected into thereturn passage leading to the advanced stage impeller.

This invention relates to an arrangement for installing and operatinginlet guide vanes for the successive stages of a high pressure,centrifugal, refrigerant compressor. Adjustable guide vanes on stagesother than the first stage of a multiple stage compressor offer theadvantages of betterperformance and capacity range. The positioning ofthe guide vanes at each stage of compression determines the totalcapacity developed by the compressor. Better capacity control,especially under light load conditions, could be achieved by utilizingadjustable guide vanes at each compression stage. However, assemblyproblems and the additional space required to accommodate the linkagemechanism for guide vanes at each impeller inlet have generallydiscouraged the use of adjustable guide vanes at advanced stages ofcompression. Also, the additional linkages and operating shafts requiredfor such an adjustable guide vane arrangement have presented complicatedseal problems.

By virtue of a unique operating shaft and linkage location andarrangement, the present invention overcomes the aforesaid problems inproviding adjustable guide vane control at each stage of a multiplestage refrigerant compressor. The centrifugal compressor of thisinvention is designed to compress refrigerant gas in a refrigerationsystem comprising a compressor, condenser, economizer, and evaporatorinterconnected in refrigerant flow relationship. The economizer is achamber normally located between the condenser and the evaporator inwhich the pressure of the liquid refrigerant is reduced before it entersthe evaporator. Pressure reduction in the economizer causes a portion ofthe liquid to fiash to vapor, thereby cooling the remaining liquid. Theflash gas from the economizer is normally directed to an intermediatepressure stage of the multiple stage refrigerant compressor. Ourimproved compressor design incorporates a chamber between the returnpassage leading to an advanced stage of compression and the diffuserpassage connected to the outlet thereof. This chamber serves the dualpurpose of accommodating the linkage mechanism for the adjustable guidevanes at the inlet to the advanced stage of compression and also actingas a plenum chamber from which ice economizer gas may be introduced intosaid return passage.

A particularly advantageous feature of this invention lies in thedisposition of the interstage crossover passage between successivestages of compression radially inwardly from the outer casing of thecompressor. This provides a space between the crossover passage and theouter casing through which the operating shaft for an advanced stagevane linkage mechanism may extend. By thus avoiding passing the guidevane operating shaft through any portion of the interstage crossoverpassage the number of seals required along the operating shaft isreduced to a minimum.

These and other advantageous features of our invention will becomereadily apparent as the following description is read in conjunctionwith the accompanying drawings.

FIGURE 1 is a front elevation view, partially in section, showing acentrifiugal compressor embodying the guide vane actuating mechanism ofthis invention.

FIGURE 2 is a vertical section view taken along line 22 of FIGURE 1.

FIGURE 3 is a vertical section view taken along line 33 of FIGURE 1showing the first adjustable guide vane actuating mechanism,

FIGURE 4 is an enlarged fragmentary view of a portion of the guide vaneactuating mechanism for the second stage.

FIGURE 5 is a schematic illustration of a refrigeration system employingthe compressor of the present invention.

With reference to FIGURE 1 of the drawings, the multiple stagecompressor of this invention is comprised of an outer casing 1 throughwhich a drive shaft 4 extends longitudinally. Shaft 4 may be driven byany con venient means such as an electric motor or a turbine. Forpurposes of illustration, two axially spaced impeller wheels 6 and 10are shown mounted upon drive shaft 4. Casing 1 could obviously beenlarged so as to house a larger number of impeller wheels and therebyprovide greater compressor capacity. Secured to each of the impellerwheels 6 and 10 are a plurality of blades 8 and 12 which extend radiallyoutwardly to the peripheral discharge area of each of said wheels. Aninternal wall generally indicated by reference numeral 14 defines acrossover passage 15 which connects the outlet of first stage impeller 6with the inlet of second stage impeller 10. A first radially extendingportion 16 of wall 14 bounds a discharge passage 18 for impeller 6. Asecond radially extending portion 20 of wall 14 encloses return section22 of crossover passage 15. Diffuser plate 24 bounds discharge passage25 communicating with the peripheral outlet of second stage impeller 10.Refrigerant gas passing radially outwardly through discharge passage 25is collected in annular chamber 26 from which it is directed out of thecompressor casing through discharge pipe 28 shown in FIGURE 5.

Refrigerant gas is introduced into compressor casing 1 through suctionpipe 30. Suction inlet passage 32 bounded by suction plate 34 serves todirect incoming refrigerant gas radially inwardly and then axially intothe inlet of first stage impeller Wheel 6. Adjustable guide vanes 36located in suction inlet passage 32 operate to control the capacity offirst stage impeller 6 and to give the desired pre-rotation to theinfiowing refrigerant gas. Vanes 36 are disposed around the entirecircumference of inlet passage 32 and are rotatably mounted on pins 38.A second set of adjustable guide vanes 40 are rotatably mounted inreturn passage 22 leading to the inlet of second stage impeller 10.

With reference to FIGURES 1 and 3, first stage guide vanes 36 areactuated by a linkage mechanism generally indicated by reference numeral42. Mechanism 42 includes levers 44 which turn vane pins 38 and areoperated by rods 46 connected to ring 48. Three equally spaced rollers50 (only one of which is shown) rotatably support ring 48. Lever 52 forring 48 is actuated by connecting rod 54 attached to crank 56. Theaforesaid linkage mechanism is driven by an operating shaft arrangementcomprised of a first operating shaft section 58 and a second section 60.One end of shaft section 58 extends through seal housing 62 in outercasing 2 to a point of connection with external actuating crank 64.Leakage of refrigerant gas outwardly along shaft section 58 is preventedby spring-loaded graphite seal 66. Control apparatus responsive to thecooling load on the refrigeration system in which compressor 1 isinstalled may be employed to actuate crank 64. Such a controlarrangement is shown in US. Patent No. 2,955,436.

Operating shaft section 58 extends inwardly through bearing bracket 68,and is secured at its inner end to crank 70. Rod 72 connects cranks 70and 56. The rotation of first operating shaft section 58 and crank 70therewith actuates interconnected crank 56, and first stage vane linkage42 connected thereto. In this manner, first stage guide vanes 36 areadjusted to the proper position in response to the load sensing deviceconnected to external crank 64.

As first stage linkage crank 56 rotates, it turns second operating shaftsection 60 to which it is fixedly secured. This permits the synchronousactuation of second stage vane linkage 74 which is connected to theinner end of operating shaft section 60. Linkage 74 is comprised of thesame basic elements as described above with respect to first stagelinkage 42. Referring now to FIGURES l and 2, this includes vane turninglevers 76 connected by rods 78 to synchronizing ring 80. Ring 80 isrotated on rollers 82 by lever 84. Movement is imparted to lever 84 byconnecting rod 86, which is secured to crank 88 for actuation thereby.Crank 88 is secured to second operating shaft section 60 for rotationtherewith. Sleeve bearing 92 mounted in bearing bracket 94 supportsshaft section 60 at its inner end. As is indicated in FIGURE 1, bearingbracket 94 is fastened to diffuser plate 24.

FIGURE 4 shows the final drive portion of second stage linkage mechanism74 on an enlarged scale. Second stage guide vanes 40 are pivotallymounted on pins 90 connected to levers 76. As connecting rods 78 aremoved by the rotation of ring 80', the pivot levers 76, and vane pins90.

FIGURE illustrates the manner in which compressor 1 would normally beconnected in a refrigeration circuit. Refrigerant vapor from evaporator96 is drawn into compressor 1 through suction pipe 30, progressivelyraised in pressure as it passes through the successive impeller wheelsand internal passages, and discharged through pipe 28. The compressedrefrigerant gas flows through discharge pipe 28 into condenser 100 whereit is cooled and condensed to the liquid state by a cooling mediumpassing through condenser coil 101. Liquid refrigerant flows out ofcondenser 100 through liquid line 102 to economizer vessel 104. Therefrigerant liquid flashes to an intermediate pressure in economizer104, as a result of which a certain amount of flash gas is formed,thereby cooling the main body of refrigerant liquid. The chilledrefrigerant liquid is directed through pipe 106 and valve 107 toevaporator 96 where it vaporizes to produce the desired cooling effecton a secondary liquid such as water flowing through coil 108. The flashvapor formed in economizer 104 passes through pipe 110 into casing 2 ofcompressor 1.

As is shown in FIGURE 1, the economizer gas entering compressor 1 isreceived in chamber 112 formed Within casing 2 between second stagediffuser plate 24 and radially extending portion of wall 14. A pluralityof nozzles 114 in wall portion 20 conduct economizer gas from chamber112 into passage 22 leading to second stage impeller wheel 10. Chamber112 thus serves as an economizer gas plenum chamber as well as a housingfor second stage guide vane linkage mechanism 74.

Wall assembly 14 includes a solid section 116 located between crossoverpassage 15 and outer casing 2. Operating shaft section 60 extendsthrough solid section 116 radially outwardly from crossover passage 15into economizer gas chamber 112. Since shaft section 60 does not passthrough any portion of crossover passage 15, the problem of providingseals to prevent interstage leakage of refrigerant gas along shaftsection 60 is greatly minimized. Leakage can only take place fromrelatively higher pressure economizer chamber 112 along shaft section 60into space 33 adjacent first stage suction inlet passage 32. Suchleakage is prevented by a single seal 118 positioned between shaftsection 60 and wall section 116.

The assembly procedure is simplified by using two operating shaftsections 58 and 60 rather than one. Section 60 may be inserted throughwall section 116 and crank 88 into bearing 92 and aligned in bearingbracket 68 with end cover assembly 3 removed. After first stage linkage42 is installed and end cover assembly 3 mounted on casing 2, firstoperating shaft section 58 is inserted through bearing housing 62. Thealignment of short shaft section 58 in bearing bracket 68 and themounting of crank 70 on its inner end is a relatively simple operation.It would be considerably more diflicult to align a single, longoperating shaft within the several spaced bearings and seals in casing 2and connect it to cranks 56 and 88 than to install separate, shortsections 58 and 60.

We claim:

1. A multiple stage refrigerant compressor comprising:

an outer casing;

a drive shaft extending through said casing;

a plurality of Centrifugal impeller wheels mounted on said drive shaftin axially spaced relationship;

wall means within said outer casing defining a cross over passage havinga diffuser portion and a return portion connecting the outlet of one ofsaid impeller wheels with the inlet of the next one of said impellerwheels;

a first set of adjustable guide vanes in the suction inlet of said oneof said impeller wheels;

a second set of adjustable guide vanes in the suction inlet of said nextone of said impeller wheels;

operating shaft means extending within said outer casing through saidwall means radially outwardly from said crossover passage, said shaftmeans having one end portion which passes through said outer casing to apoint of connection with external actuating means;

first and second linkage mechanisms operatively connected to said firstand second sets of adjustable guide vanes, each of said linkagemechanisms including a crank fixedly secured to said operating shaftmeans for rotation therewith;

a diffuser plate bounding a diffuser passage communicating with theoutlet of said next one of said impeller wheels, said diffuser platebeing spaced from said return portion of said wall means so as to definetherebetween a chamber within which said second linkage mechanismconnected to said second set of adjustable guide vanes is located.

2. A compressor as defined in claim 1 wherein:

said operating shaft means is rotatably supported at the opposite endportion thereof by a bearing mounted on said diffuser plate.

3. A compressor as defined in claim 1 wherein:

said chamber is bounded at its outer extremity by said outer casing; and

said crank of said linkage mechanism for said second set of adjustableguide vanes extends within said chamber in a direction generally normalto said operating shaft means to a point of connection therewith in theportion of said chamber adjacent the inside of said outer casing.

4. A compressor as defined in claim 1 wherein:

said operating shaft means is comprised of first and second sections,said first section including said end portion which passes through saidouter casing; and

said cranks of said first and second linkage mechanisms being secured tosaid second section.

5. A compressor as defined in claim 4 and further including:

linkage means drivingly connecting said first section of said operatingshaft means to said crank of said first linkage mechanism.

6. A compressor as defined in claim 1 and further including:

a suction plate bounding a suction inlet passage to said one of saidimpeller wheels; and

wherein said first linkage mechanism is located outside of said suctioninlet passage between said suction plate and one end of said casing in aregion where it does not interfere with gas flowing into and throughsaid suction inlet passage.

7. In combination with a condenser, economizer, flow regulating meansand an evaporator interconnected in a closed refrigeration circuit, animproved centrifugal compressor connected in said circuit between saidevaporator and said condenser and comprising:

an outer casing;

a drive shaft extending through said casing;

a plurality of centrifugal impeller wheels mounted on said drive shaftin axially spaced relationship;

wall means within said outer casing defining a crossover passageconnecting the outlet of one of said impeller wheels with the inlet of afollowing one of said impeller wheels, said wall means including a firstsubstantially radially extending portion bounding a discharge section ofsaid crossover passage and a second substantially radially extendingportion :bounding a return section of said crossover passage; a diffuserplate enclosing a diffuser passage communicating with the outlet of saidfollowing one of said impeller wheels, said diffuser plate being spacedfrom said second radially extending portion of said wall means so as toprovide a chamber therebetween;

a first set of adjustable guide vanes in the suction inlet of said oneof said impeller wheels; a second set of adjustable guide vanes in thesuction inlet of said following one of said impeller wheels;

first and second linkage mechanisms operatively connected to said firstand second sets of adjustable guide vanes, said second linkage mechanismbeing located in said chamber;

10 end portion which passes through said outer casing to a point ofconnection with external actuating means, and each of said first andsecond linkage mechanism being operatively connected to said shaft 5means for synchronous actuation thereby.

9. Refrigeration apparatus as defined in claim 8 wherein:

said wall means includes a solid section disposed between said crossoverpassage and said outer casing which separates said chamber from a spacewithin said outer casing adjacent said suction inlet of said one of saidimpeller wheels; and wherein said operating shaft means passes from saidspace through said solid section into said chamber; and furtherincluding a seal between said operating shaft means and said solidsection arranged to prevent leakage of refrigerant gas from said chamberinto said space. 30 i0. Refrigeration apparatus as defined in claim 8wheresaid operating shaft means is comprised of first and secondsections, said first section including said end portion which passesthrough said outer casing, and said second section being connected tosaid first and second linkage mechanisms.

References Cited UNITED STATES PATENTS MEYER PERLIN, Primary Examiner s.c1. X.R,. 230-114

